Biogeography of Eight Large Branchiopods Endemic to California BRENT P. H ELM Jones & Stokes Associates, Inc., 2600 V Street, Sacramento, CA USA 95818 CURRENT ADDRESS: 5998 Windbreaker Way, Sacramento, CA 95823 ([email protected]) ABSTRACT. Northern California supports eight endemic species of large branchiopods (Crustacea: Anostraca, Notostraca, and Conchostraca), three of which are listed as endangered and one as threatened under the federal Endangered Species Act. Published information on the geographic distribution of these endemics from a biological perspective is scant. This study was initiated to gain a better understanding of the biogeographic distribution and abundance of endemic large branchiopods in California. The primary objective was to investigate several physical features of wetlands that change little over time (e.g., habitat type, potential maximum and average ponding depth, potential maximum ponding surface area and water volume, soil type, and landform) for correlations to species’ presence or absence. The secondary objective was to analyze selected life cycle dynamics (i.e., maximum population longevity, and minimum, mean, and maximum age to maturation and repro- duction) for correlations to habitat characteristics. These objectives were accomplished by gathering and analyzing quanti- tative data on 5,565 wetlands studied in California between 1989 and 1996, and on endemic large branchiopods raised in mesocosms (plastic wading pools) between 1990 and 1996. Large branchiopods were found in slightly less than half the seasonal wetlands sampled during field surveys. Anostracans comprised the majority of these. The three most common large branchiopod species were Lepidurus packardi, Linderiella occidentalis, and Branchinecta lynchi. Endemic species occurred in half the 50-wetland types and on most landforms sampled. Approximately two-thirds of the wetlands sampled were vernal pools. Vernal pools supported a higher percentage of large branchiopod occurrences, and species richness, than any other wetland type. The majority of occurrences of B. lynchi and L. occidentalis are located on High Terrace landforms with Redding, Corning, or Red Bluff soils; these land- forms also supported slightly more than half the occurrences of L. packardi. Life cycle analyses of cultured populations revealed that the Midvalley Fairy Shrimp (Branchinecta sp. – not described or named) has the fastest maturation period, followed by B. lynchi, B. conservatio, B. longiantenna, Linderiella occidentalis, Lepidurus packardi, and Cyzicus californicus. Overall, the seven species differed significantly in age of first reproduction (ANOVA:F6,89 = 6.75, P < 0.0001), and maximum population longevity (ANOVA:F6,89 = 15.50, P < 0.0001). However, a multiple range test revealed the anostracans did not differ significantly among each other in age at first reproduction and that Lepidurus packardi did not differ significantly from C. californicus and the four anostracan species: Midvalley Fairy Shrimp, L. occidentalis, B. longiantenna, and B. conservatio. Nonetheless, the age at first reproduction for C. californicus was significantly later than that of anostracan species. Physical wetland parameters (i.e., mean average ponding depth, mean maximum ponding depth, mean maximum ponding surface area, and mean maximum ponding volume) were utilized as predictors to assess the responses of life cycle data (i.e., mean maturation period, mean reproduction period, and mean population longevity period) using linear regression best subsets. Significant linear correlations were obtained when: mean maximum ponding surface area and mean maximum ponding volume were used to predict the response of mean maturation period (F2,4 = 18.71, P < 0.009); mean average ponding depth, mean maximum ponding depth, mean maximum ponding surface area ,and mean maximum ponding volume were used to predict the response of mean reproduction period (F4,2 = 102.24, P < 0.010); and mean maximum ponding surface area and mean maximum volume were used to predict the re- sponse of mean population longevity period (F2,4 = 7.39, P < 0.045). CITATION. Pages 124-139 in: C.W. Witham, E.T. Bauder, D. Belk, W.R. Ferren Jr., and R. Ornduff (Editors). Ecology, Conservation, and Management of Vernal Pool Ecosystems – Proceedings from a 1996 Conference. California Native Plant Society, Sacramento, CA. 1998. 124 BIOGEOGRAPHY OF EIGHT LARGE BRANCHIOPODS ENDEMIC TO CALIFORNIA INTRODUCTION TABLE 1. Large branchiopods (Crustacea: Branchiopoda) occurring in northern California. Excluding the two brine shrimp species (Artemia monica Verrill and A. franciscana Kellogg), Northern California (i.e., north of Anostraca (Fairy Shrimp) 37° latitude) supports 21 species of large branchiopods, eight being endemic to the state (Longhurst, 1955; Martin and Belk, Branchinecta dissimilis (Dissimilar Fairy Shrimp) Branchinecta coloradensis (Colorado Fairy Shrimp) 1988; Eng et al., 1990; Rogers, 1996) (Table 1). These endemic Branchinecta conservatio (Conservancy Fairy Shrimp)* E species include five Anostraca (fairy shrimp): Linderiella Branchinecta gigas (Giant Fairy Shrimp) occidentalis (Dodds), Branchinecta conservatio Eng, Belk and Branchinecta lindahli (Versatile Fairy Shrimp) Eriksen, B. longiantenna Eng, Belk and Eriksen, B. lynchi Eng, Branchinecta longiantenna (Longhorn Fairy Shrimp)* E Belk and Eriksen, and Midvalley Fairy Shrimp (Branchinecta Branchinecta lynchi (Vernal Pool Fairy Shrimp)* T sp. - not described or named). Two are Notostraca (tadpole Branchinecta mackini (Alkali Fairy Shrimp) shrimp), Lepidurus packardi Simon and Lepidurus sp., a po- Branchinecta sp. (Midvalley Fairy Shrimp)* tential new species (J. King, pers. comm.) referred to as the Eubranchipus bundyi (Knobbedlip Fairy Shrimp) Modoc Plateau Tadpole Shrimp; and one is a Conchostraca (clam Eubranchipus oregonus (Oregon Fairy Shrimp) shrimp), Cyzicus californicus Packard. Dr. Clay Sassaman (pers. Eubranchipus serratus (Ethologist Fairy Shrimp) comm.) is currently working on the genetics of Cyzicus and has Linderiella occidentalis (California Fairy Shrimp)* suggested that C. californicus and C. elongatus may be the same Streptocephalus sealii (Spiney tail Fairy Shrimp) animal. Therefore, Cyzicus species occurring in the Coast Range Conchostraca (Clam Shrimp) (C. californicus) and Central Valley (C. elongatus) were con- sidered to be C. californicus for purposes of this paper. Lepidurus Cyzicus californicus (California Clam Shrimp)* packardi, Branchinecta conservatio, and B. longiantenna have Lynceus branchiurus (Lentil Clam Shrimp) been listed as endangered and B. lynchi as threatened under the Notostraca (Tadpole Shrimp) federal Endangered Species Act (ESA) by the U.S. Fish and Wildlife Service (USFWS) (59 Federal Register 48136) (Table Lepidurus cousei (Intermountain Tadpole Shrimp) 1). Lepidurus lemmoni (Alkali Tadpole Shrimp) Lepidurus packardi (Vernal Pool Tadpole Shrimp)* E Lepidurus sp. (Modoc Plateau Tadpole Shrimp)* In 1989, before Eng et al. (1990) had described the three feder- Triops longicaudatus (American Tadpole Shrimp) ally listed endemic anostracans as species; little information was available about their biology and distribution. For this rea- * = endemic, E = Endangered, T = Threatened son, Jones & Stokes Associates biologists initiated standard- ized data collection techniques to acquire information about potential and occupied large branchiopod habitats regarding water chemistry, plant species composition and abundance, Vernal pool habitat was simulated in mesocosms (plastic wad- wetland type, potential maximum and average ponding depth, ing pools) maintained out-of-doors in Sacramento, Sacramento potential maximum ponding surface area, soil type, and land- County, California from 1990 to 1996. Large branchiopod popu- form. It became apparent early in the investigation that water lation samples from various sites throughout California were chemistry parameters were not strong indicators of the poten- transplanted to these pools and life-history data, including age tial presence or absence of large branchiopod species because at first maturation and reproduction, and maximum population wetland water chemistry fluctuates widely, both daily and sea- longevity were collected for each species. Life cycle data on sonally, and largely reflects local surface weather conditions seven endemic large branchiopod species were analyzed to de- (e.g., air temperature, rainfall, and wind speed and direction), termine whether species differ in age at first maturation and photosynthesis, and soil properties. In addition, analysis of ver- reproduction, and maximum population longevity. Differences nal pool vegetation composition as a predictor of presence (or in age at first maturation and reproduction, and maximum lon- presumed absence) of large branchiopods yielded little corre- gevity may determine differences in large branchiopod species lation. Therefore, we focused on physical features of the sea- distributions among wetlands with different ponding durations. sonal wetland, that change little if any with time, to assess species Analysis of data collected by Jones & Stokes Associates (1996) presence. Features chosen were habitat type, potential maxi- on depth, size, volume, and duration of ponding of created and mum and average ponding depth, potential maximum ponding natural vernal pools indicate a very strong correlation of ponding surface area and water volume, soil type, and landform. This duration to wetland depth, size, and volume.